Today, we talk about germs. The University of
Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
created them.

That great master of American
doggerel, Ogden Nash, wrote:

A mighty creature is the germ,
Though smaller than the pachyderm,
His strange delight he often pleases,
By giving people strange diseases.

Our knowledge of microbes is only three hundred
years old. The Dutch lens maker Antonj Leeuwenhoek first observed
them in the late 17th century. He called these
small creatures animalcules, and he realized
that they swam in any body of water.

But what about relating these small beasts to
disease? A hundred and fifty years later, disease
was rampant in London. Half the newborn babies
died, and the death rate was far higher among the
poor than the wealthy. Two things were clear by
then. One was that London's drinking waters were,
by and large, loaded with microorganisms. The other
is that filth, particularly raw sewage, was to be
found everywhere in poor areas.

It seems obvious to us that germs were causing the
diseases. But germs, after all, swam in waters
drunk by the well and the sick alike. Bad smells,
on the other hand, were found in unhealthy
neighborhoods, so people assumed that stench, or
miasma, as it was
called, caused disease. No one saw any reason to
worry about the water. It was the stink people felt
they had to get rid of.

Then, in 1849 and '53, London suffered terrible
epidemics of cholera. A physician, John Snow, began
looking at statistics. He worked doggedly among the
sick and kept meticulous records of who'd died and
exactly where they'd died. It took a long time, but
Snow eventually found a high incidence of cholera
among people who'd been drawing water from a pump
called the Broad Street Well.

That made no particular sense until Snow realized
that the cesspool of a tenement occupied by a
cholera patient was next to the well. Contaminated
water had leaked from the cesspool into the well's
ground-water. Over protests, he managed to remove
the handle from the well, and cholera abated in
that part of London.

Snow's report soon led people to see that cholera
was not caused by noxious gases, but by what was
now called fecalized water. He put people on the
track of the real agent of the disease. Four years
later, Pasteur connected disease to bacteria. In
1865 Joseph Lister found he could kill
disease-carrying bacteria during surgery by
spraying a carbolic acid solution over the patient.
Finally, thirty years after Snow pinpointed the
Broad Street Well, the German physician Robert Koch
showed how to make a disease-specific vaccine. He
isolated the bacterium that caused anthrax and
figured out how to make a vaccine to kill it.

It can take decades to overturn old thinking. The
leap from unhealthy vapors to bacteria was still
hard to make -- even after Snow used the Broad
Street Well to show that a leap had to be made.

I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.

(Theme music)

A simple account of Snow's work is to be found in:
Dubos, R., and Pines, M., Health and Disease.
New York: Time-Life Books, 1965.

For a fascinating fictionalized account of John
Snow and the Broad Street Well, see: Taylor, L. P.,
The Drummer was the First to Die. New York:
St. Martins Press, 1992.